10
Example: 750/760 = 0.9868 x 100 = 98.68% calibration value when
DO Local is disabled.
When DO Local% is enabled, the Pro20/Pro20i corrects for barometric
pressure for each DO measurement instead of during calibration.
Example:
Instrument #1 with DO Local% enabled:
At 737 mmHg barometric pressure, roughly 841 ft above sea level, the
instrument would calibrate to 100%.
When taking measurements at the same location (737 mmHg) in a 20°C
fresh water sample that is completely air-saturated, the instrument
would read:
DO %L value = 100%
DO mg/L value = 8.81 mg/L (9.09
1
x .9697
2
)
Instrument #2 DO Local% disabled:
At 737 mmHg barometric pressure, roughly 841 ft above sea level, the
instrument would calibrate to 737/760 x 100% = 96.97%
When taking measurements at the same location (737 mmHg) in a 20°C
fresh water sample that is completely air-saturated, the instrument
would read:
DO% value = 96.97%
DO mg/L value = 8.81 mg/L (9.09
1
x .9697
2
)
Hence, the mg/L readings are unaffected by DO Local%.
1.) Value from oxygen solubility table (Appendix B).
2.) 737/760 x 100%, correction for barometric pressure.
LAST DIGIT SUPPRESSION (LDS)
Last Digit Suppression (LDS)
can be enabled or disabled by using the
up or down arrow keys to highlight it and pressing enter
. An ‘X’ in
the box next to LDS indicates it is enabled.
LDS rounds the DO value to the nearest tenth; i.e. 8.25 mg/L becomes
8.3 mg/L. LDS is automatically disabled during calibrations.
